Load-Bearing Wall Construction
In conventional construction of multi-storey structures comprising load-bearing walls, platform framing technique is used. As the name suggests, platform framing relies on the floor assembly to provide a platform for subsequent framing construction. The lower floor supporting elements, usually the load-bearing walls, are constructed, then the floor elements installed, directly bearing on the supporting elements below. The follow-up bearing walls are then constructed, followed by the next upper floor assembly. The process repeats itself until the roof elements are installed. All modern floor systems involve the use of concrete as an integral part of the floor assembly. The fact that subsequent floor construction follows the completion of the floor assembly below means a significant delay in waiting for the concrete to cure.
Attempts have been made to eliminate/minimize the delay in platform construction. U.S. Pat. No. 4,486,993 by Graham et al, No. 5,881,516 by Luedtke, and U.S. Pat. No. 5,782,047 as well as U.S. Pat. No. 6,298,617 by de Quesada, deal, in varying degrees, with methods of constructing bearing walls whereby the upper wall assembly can proceed before completion of the floor elements.
The first one, U.S. Pat. No. 4,486,993 by Graham et al, employs hot rolled angles attached to a foam-core latticed bearing wall for floor assembly support.
U.S. Pat. No. 5,782,047 by de Quesada employs hot rolled ledge angles attached to light gauge C-shaped channel steel stud bearing walls for bearing support of the concrete-topped floor assemblies. Floor concrete may terminate at the sides of the load-bearing walls, or may be carried continuously between the upper and lower wall assemblies. In the latter case (with concrete running between upper and lower assemblies), the upper wall assembly is supported on equally spaced screw-jack assemblies allowing the upper wall assembly to proceed before the floor concrete.
In U.S. Pat. No. 6,298,417, de Quesada refined his earlier invention and discarded the use of hot rolled ledge angles for floor support, and screw-assemblies as spacers to allow continuity of the concrete in the floor. In place of the hot-rolled ledge angles, a hat section is placed on top of the lower wall panel, with legs projecting horizontally out to support floor joists. In place of screw-jack assemblies, discrete connectors are used. These connectors are shop-welded to the bottom of the upper wall panel, and site welded to the top of the bottom panel.
U.S. Pat. No. 5,881,516 by Luedtke deals with load bearing wall systems wherein the axial load does not pass through the floor assembly. Wall systems include both wood and conventional steel stud bearing walls. Floor assemblies include wood joists, light gauge steel C-joists, and low-profile composite steel decks. The floor assemblies are supported, outside of the plane of the bearing wall, by various metal devices.
Underlying all of the above-referenced U.S. Patent Documents is the premise of carrying the floor load outside of the plane of the bearing wall. This very premise, however, creates eccentricity in the loading, and significantly reduces the load carrying capacity of the bearing wall. Both Luedtke (U.S. Pat. No. 5,981,516) and de Quesada (U.S. Pat. Nos. 5,782,047 and 6,298,417) deals with shallow floor assemblies, i.e. low-profile floor decks (less than 76 mm in depth) and C-joists. The more common steel floor systems with OWSJ and medium/deep (in excess of 76 mm in depth) profile composite-floor-decks are not discussed. With significantly increased spans associated with these more common systems, the eccentric bearing details become costly and complicated.
While continuity of the concrete in the floor assembly is maintained within the plane of the load bearing walls to maintain continuous inter-floor fire and acoustic separation across the bearing walls, neither Luedtke (U.S. Pat. No. 5,881,516) nor Graham (U.S. Pat. Nos. 5,782,047 and 6,298,417) makes structural use of the concrete. Hence, secondary structural elements are still required over window or door openings in the wall panels.
This invention will present metal stud load-bearing wall systems that                Permit upper floor-wall assemblies to proceed prior to installing floor concrete;        Support metal C-joists, open web steel joists, deep profile steel decks (over 50 mm in depth) without eccentric loading; and,        In the case of the load-bearing walls supporting OWSJ and C-joists, embody a reinforced concrete beam at the floor level as part of the wall systems        
Composite Beam Supporting Open Web Steel Joists
In post-and-beam construction with OWSJ's, floor joists bear directly on the supporting beams, thus creating a space between the floor concrete and the supporting beams. This bearing detail is the only reason precluding the use of composite beam construction in the steel-joist-on-beam construction.
Rongoe (U.S. Pat. No. 4,741,138 and Canadian Patent 1,230,495) solved this problem by providing extensions from the girder, through the decking and into the concrete, in an assembly utilizing girders, standard joists bearing on top of the girders, and metal decking onto which concrete is poured. The extensions are located in between open web steel joists. The shear headed studs are field welded to the extensions through holes cut in the steel deck.
The limitations of this composite girder are:                The thickness of cover concrete available for composite action; and        Expense of the extension and the amount of welding required for composite action.        
This invention provides an intermediate bearing element to support the joists and allows for the floor concrete to be in full contact with the steel beam along the full length of the beam. Instead of merely adding a thin concrete deck acting compositely with the steel beam, this invention provides a deep concrete section (T-section for interior beam and L-section for perimeter beam, respectively) to act integrally with the steel beam. This invention allows shop installation of headed studs to the beam for better quality control.
Shear-Connection-Ready Open Web Steel Joists
Concrete-topped steel deck on open web steel joists constitutes the most common steel floor system. Many attempts have been made to further the efficiency of the system by integrating the open web steel joists with the concrete on the steel deck for composite action.
McManus (U.S. Pat. No. 4,189,883), and Moreau (Canadian Patent Documents 2,441,737 and 2,404,535) reveal means of integrating the top chord of open web steel joists and/or trusses with the concrete deck for improved horizontal shear resistance.
Dutil (U.S. Pat. No. 5,544,464), Taft (U.S. Pat. Nos. 4,653,237 and 4,432,178, and Canadian Patent 1,208,030), and Gjelsvik et al (Canadian Patents 1,251,056 and 1,186,910) all present composite open web steel joist systems working in concert with concrete-topped steel decks for greater gravity load-carrying capacity. This invention is mainly concerned with the gravity load-carrying capacity of the composite open web steel joist system.
In Dutil's system, each joist has a top chord forming a shear connector protruding into the concrete deck. Forming part of the top chord are two angles acting as shelves to receive steel decking. The deck acts as a form for pouring the slab, and is a permanent part of the composite floor system. Dutil's system is commercially marketed under the name of Hambro joists by Canam.
Taft introduced a secondary truss-type framing member in which the top chord of the truss is formed in the shape of a modified “I” section having an upper flange, web and lower flange for supporting steel decking. The upper flange and web of the top chord are totally embedded in the concrete to cause the concrete floor and steel truss to function together structurally as a composite system.
Gjelsvik et al proposed open web steel joists with the top chord comprising a pair of steel angles, and web members extending between the steel angles to the top of the vertical legs of the steel angles. Decking is supported by the horizontal legs of the top chord of adjacent joists and a concrete slab poured on the decking and between the vertical legs of the top chord to provide bonding between the concrete slab, top chord and web.
All the above systems exhibit the common features:                Steel deck is supported by shelves forming part of the joist top chord, and is discontinuous over the joist.        Composite action is achieved by embedding the top chord in the concrete, which acts as a continuous shear connector.        
The use of shelves (usually in the form of angles) for deck support increases the cost of the composite open web joist system in several ways:                Expensive shelve angles        Discontinuous steel deck        Excessive connections over joist support        Slower deck installation        
This invention will show how the expensive shelves (usually in the form of angles) may be eliminated and the continuity of the steel deck maintained with field-installed discrete shear connectors onto a new type of shear-connection-ready OWSJ.
Perimeter Stud Walls With Improved Impact Resistance
In post-and-beam construction, perimeter walls are often in-filled walls with metal studs. The in-fill walls are normally deigned against wind loads only. In load-bearing metal stud wall construction, the perimeter walls are designed for gravity load as well as wind loads. In either case, perimeter stud walls are not designed for errant vehicles running into buildings. This invention will show an economical method of constructing perimeter metal stud walls with improved resistance to impact from errant vehicles.